Kistler-Morse KM STXPlus - Manual (Page 13)

CHAPTER 3: STAND-ALONE ANALOG CALIBRATION AND SET UP
NOTE
If you do not press a button within
15 seconds the STXplus exits the
programming mode. Once step 3 has been
completed above, the LO Span value will be
restored.
Starting with a Full Vessel
1. Empty the vessel completely.
2. Press the DOWN or UP buttons until the
PARAM LEDs look like:
Press the ENTER button.
3. Press the UP or DOWN buttons until
the appropriate current output is achieved
(20mA if in 4-20mA or 0-20mA mode,
4mA if in 20-4mA mode or 0mA if
in 20-0mA mode). Press the ENTER
button.
4. Empty the vessel.
5. Press the DOWN or UP buttons until the
PARAM LEDs look like:
Press the ENTER button.
6. Press the UP or DOWN buttons until the
appropriate current output is achieved
(0mA if in 0-20mA mode, 4mA if in
4-20mA mode, or 20mA if in either
20-4mA mode or 20-0mA mode). Press
the ENTER button.
Figure 3-3. Calibration by Adding a Known
Quantity of Material.
NOTE
If you do not press a button within
15 seconds the STXplus exits the
programming mode. Once step 3 has been
completed above, the HI Span value will be
restored.
Calibration by Adding or Subtracting a
Known Quantity of Material
This calibration method does not require the
vessel to be completely empty.
LO Span (See (1) in Figure 3-3) is set to the
expected current output. A known quantity
of material, representing at least 25% of the
vessel’s total capacity, is added to the
vessel. HI Span (See (2) in Figure 3-3) is set
to the expected current output. Points (1)
and (2) define the straight line. The slope
of the line is call the Scale Factor, which is
calculated internally. Zero (See (3) in Figure
3-3) is calculated.
The calibration is reasonably accurate
because it is based on the known difference
between the currents (based on the
difference in weights) and counts. However,
if the estimated weight is incorrect, the
actual location of the line is incorrect,
resulting in errors in output. The greater the
error in the estimated weight, the greater the
resulting error.
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